Which of the following actions best exemplifies jettison?

The action that best exemplifies jettison is throwing cargo overboard to prevent sinking. Jettisoning refers specifically to the act of discarding or throwing away parts of a load, typically cargo, from a vessel to lighten the ship and improve its stability and buoyancy. This practice is often used in emergency situations where the ship may be in danger of sinking due to overloading or water intake. By removing weight, the ship can regain its ability to float and navigate more safely.

The other choices do not accurately represent the concept of jettisoning. Running aground to save the ship is a maneuver that involves intentionally beaching the vessel, which is a strategic decision rather than discarding cargo. Delaying arrival to avoid rough seas is about timing and weather considerations, not about disposing of weight. Similarly, sealing ship margins to avoid leakage focuses on repairing and maintaining the vessel's integrity rather than removing cargo. These actions are preventative or reactive in nature but do not convey the act of discarding cargo to alleviate a critical situation maritime crews often face.